Protection method and system for equipment in a network element

ABSTRACT

A protection method and system for equipment in a network element receives a protection request for an equipment item. A priority of the request and a priority of the equipment item is evaluated relative to all other outstanding protection requests for equipment items in a protection group with the equipment item. A highest priority protection request for a highest priority equipment item is performed.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.09/658,165, filed Sep. 8, 2000, now U.S. Pat. No. 6,906,997 by RaghuRajan et al. and entitled “Protection Method and System for Equipment ina Network Element”.

TECHNICAL FIELD OF THE INVENTION

This invention relates generally to the field of telecommunicationsnetworks, and more particularly, to a protection method and system forequipment in a network element.

BACKGROUND OF THE INVENTION

Telecommunications networks transmit voice and other data between endusers. The networks include switch and management nodes for processingand routing traffic in the network and links between the nodes forcarrying the traffic. The links are circuit switched or packet switchedwireline links, wireless links, or a combination of link types. Endusers communicate data over telephones, computers, personal digitalassistants (PDA) and other similar devices.

Telecommunication nodes include redundant equipment and are connected toredundant to provide fault tolerance and allow continued operation inthe event of equipment or link failure. Typically, each transmissionlink as well as line or switch cards of the nodes are backed up bycorresponding links and cards to ensure that all traffic is protected atall parts of the network. This 1+1 protection, however, is expensive tomaintain as fully half of the networks capacity is maintained inreserved for protection switching and is not used during normaloperation of the network.

To increase network efficiency, 1:N protection architectures have beendeveloped and deployed in telecommunications nodes. In thisarchitecture, a number (N) of cards or other items are protected by asingle item. Thus full protection is provided for any single failure.Multiple concurrent failures, however, cannot be completely protected.In the event of multiple concurrent failures, equipment is typicallyprotected based on a failure request priority. Within the priorities,equipment is protected on a first failed basis, which can lead to lessimportant equipment being protected at the expense of later failing,more important equipment.

SUMMARY OF THE INVENTION

The present invention provides a protection method and system forequipment in a network element of a telecommunications network thatsignificantly reduce or eliminate elements problems and disadvantagesassociated with previous systems and methods. In particular, the presentinvention prioritizes protection for failed equipment based on bothprotection request type and failed equipment type.

In accordance with one embodiment of the present invention, a method andsystem for providing protection switching for equipment in a networkelement includes receiving a protection request for an equipment item. Apriority of the request and a priority of the equipment item isevaluated relative to all other outstanding protection requests forother equipment items in a protection group with the equipment item. Ahighest priority protection request for a highest priority equipmentitem is performed.

More specifically, in accordance with a particular embodiment of thepresent invention, the equipment items in the protection group compriseline interface cards. The line interface cards may each comprise aplurality of DS-1 or other single user connections. The protectionrequest may be an activation request or a deactivation request for anequipment item.

Technical advantages of the present invention include providing animproved method and system for protecting equipment in a networkelement. In a particular embodiment, a plurality of equipment items areprotected by a single item with protection priority being provided basedon protection request type and failed equipment type. Accordingly,during multiple concurrent failures of equipment, the most importantequipment item at the highest protection request level is protected.This improves network performance and provides for a more deterministicnetwork that can be more fully controlled by network operators.

Another technical advantage of one or more embodiments of the presentinvention includes providing greater protection switching granularity.In particular, protection switching is provided for DS-1 and/or othercards supporting single connections on an 1:N basis. Thus, low levelelements may be partially protected in a network element while higherlevel elements are fully protected. This allows the majority of trafficto be fully protected while limited protection is provided forindividual flows on an efficient basis.

Other technical advantages of the present invention will be readilyapparent to one skilled in the art from the following figures,description, and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention and itsadvantages, reference is now made to the following description taken inconjunction with the accompanying drawings, wherein like referencenumerals represent like parts, in which:

FIG. 1 is a block diagram illustrating a network element for atelecommunications system in accordance with one embodiment of thepresent invention;

FIG. 2 is a block diagram illustrating details of the finite statemachine of FIG. 1 in accordance with one embodiment of the presentinvention;

FIG. 3 is a block diagram illustrating details of the state table ofFIG. 1 in accordance with one embodiment of the present invention;

FIG. 4 is a functional diagram illustrating input and output of thefinite state machine of FIG. 1 in accordance with one embodiment of thepresent invention;

FIG. 5 is a flow diagram illustrating a method for processing protectionrequest in accordance with one embodiment of the present invention; and

FIG. 6 is a flow diagram illustrating a method for evaluating protectionrequest for the method of FIG. 5 based on protection request type andequipment type in accordance with one embodiment with the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a network element 10 for a telecommunications networkin accordance with one embodiment of the present invention. Thetelecommunications network transmits voice, data, or other suitabletypes of information, and/or a combination of types of informationbetween end users. The telecommunications network may include a publicnetwork such as the Internet and the public switched telephone network(PSTN) as well as private networks such as wide area networks (WAN) andlocal area networks (LAN).

The telecommunications network includes a plurality of network elementsinterconnected by transmission links. The network elements may comprisea switch, router, add/drop multiplexer, access device or other suitabledevice capable of directing traffic in the telecommunications network.The transmission links provide the physical interface between thenetwork elements. The physical interfaces are defined by bandwidth ofthe connecting transmission links which may be DS-1 lines, DS-3 lines,OC-3 lines, OC-12 lines or other suitable bandwidths. Transmission linksmay comprise optical fiber, cable, twisted wire, or other suitablewireline or wireless links capable of transporting traffic betweennetwork elements.

Referring to FIG. 1, the network element 10 is illustrated as a add/dropmultiplexer 12 including a service complex 20, a transport complex 22, aswitch complex 24, a management complex 26, and a synchronizationcomplex 28. The complexes 20, 22, 24, 26 and 28 are interconnected byone or more buses or backplanes in the add/drop multiplexer 12.

The service complex 20 includes a plurality of 1:N protection groups 30each defining a set of working tributary cards 32 and a correspondingprotect card 34. In a particular embodiment, the 1:N protection group 30includes six (6) tributary card and a single protect card 34. It will beunderstood that the number of working tributary cards 32 in theprotection group 30 and the number of protect cards may be suitablyvaried without departing from the scope of the present invention. Theprotect card 34 is able to protect any one of the working tributarycards 32 in the protection group 30. Thus, the protect card 34 is ableto protect each of the working tributary cards 32 and to fully protectany single failure of the cards 32.

The working tributary cards 32 each receive customer input/output (I/O)and perform conversions necessary for processing by the switch complex24. In one embodiment, each tributary card 34 is a DS-1 card andreceives a plurality of DS-1 connections 36. It will be understood thatthe protection groups 30 may comprise a set of other suitable equipmentitems and/or the tributary cards 32 may receive other suitable types ofsingle user connections and/or other suitable types of aggregatedtraffic connections and/or a combination of connection types.

The transport complex 22 includes a plurality of 1+1 protection groups40. Each protection group 40 includes a working line card 42 and aprotection line card 44. Thus, the high capacity line cards 42 are fullyprotected. In a particular embodiment, the line cards 42 and 44 are OC-3or OC-12 line cards 42 that are bi-directional and perform optical toelectrical (O/E) and electrical to optical (E/O) conversions. In thisembodiment, the line cards 42 and 44 also perform overhead constructionand insertion.

The switch complex 24 comprises one or more switch fabrics for switchingtraffic between the service complex 20 and the transport complex 22 andbetween the cards within the service and transport complexes 20 and 22.In a particular embodiment, the switch complex 24 includes synchronousoptical network (SONET) and asynchronous transfer mode (ATM) switchfabrics.

The management complex 26 monitors and controls the status of theservice, transport, switch and synchronization complexes 20, 22, 24 and28. The management complex 26 also provides network managementfunctions, controls protection switching, and maintains provisiondatabases for the add/drop multiplexer 12. The synchronization complex28 synchronizes the service, transport, switch and management complexes20, 22, 24 and 26 by providing a stable traceable reference clock.

In one embodiment, the management complex 26 includes a user interface50 and a protection controller 52. The user interface 50 communicateswith network operators to allow local and remote control andprovisioning of the add/drop multiplexer 12 by the network operator andto respond to queries for information about the status of the add/dropmultiplexer 12. In a particular embodiment, the user interface 50translates requests received from a network management station (NMS) toa native format of the add/drop multiplexer 12 and forwards the requeststo the appropriate complex and/or controller for processing. In thisembodiment, the user interface 50 also converts responses and/ormessages from the add/drop multiplexer 12 to the native language of theNMS for reporting to the network operator.

The protection controller 52 receives and processes protection requestsfrom the network operator received through the user interface 50 andfrom the hardware including the service, transport and switch complexes20, 22 and 24. In response to failure of an equipment item, theprotection activation request is automatically generated locally withina complex and forwarded to the protection controller 52, an alarmforwarded to the protection controller 52 for automatic generation ofthe protection requests or otherwise suitably generated based on thestate of the hardware. Protection requests comprise activation requestsfor activation of protected equipment in case of failed or out ofservice working equipment or deactivation requests for deactivation ofprotection equipment in response to return to service of workingequipment.

In one embodiment, the protection controller 52 includes a plurality ofprotection group managers 54. Each protection group manager 54 controlsprotection requests for a corresponding protection group 30 and/or 40 onthe service and transport complexes 20 and 22. The protection groupmanagers 54 each include a finite state machine 60 and a state memory62. As used herein, the term each means everyone of at least a subset ofthe identified items. The finite state machine 60 controls activation ofprotection request for protection switching based on the state of cards32 and 34 in the protection group 30 and/or the state of cards 42 and 44in protection group 44. The state memory 62 stores the state of cards 32and 34 in the protection group 30 and/or the state of cards 42 and 44 inthe protection group 40.

The complexes, cards, protection controller 52 and other elements andequipment of the add/drop multiplexer 12 comprise logic stored assoftware encoded on a computer-readable medium for execution by ageneral purpose processor or logic stored as instructions in anapplication specific integrated circuit (ASIC), field programmable gatearray (FPGA) or other suitable medium, which may comprise one or moremedia devices and types. It will be understood that the protectioncontroller 52 may be implemented entirely on the management complex 26or its functionality distributed within the add/drop multiplexer 12.

FIG. 2 illustrates details of the tributary cards 32 the finite statemachine 60 for 1:N protection of the tributary cards 32 in accordancewith one embodiment of the present invention. In this embodiment, thefinite state machine 60 includes rules 80 specifying the priority ofrequests and the priority of cards or other suitable equipment items tobe protected in the protection group 30. Thus, the finite state machine60 may be customized for each protection group 30 and/or for protectiongroups of different equipment types.

Referring to FIG. 2, the rules 80 includes a protection requestshierarchy 82 and an equipment protection hierarchy 84. The requestshierarchy 82 includes an ascending hierarchy of request. In a particularembodiment, the request hierarchy 82 includes a highest priority offailure of protection, followed in order by lockout of protection,forced switch, failure of working and manual switch. In this embodiment,failure of protection is a failure of the protection card 34, lockout ofprotection is a lockout by the network operator of the protection card34, forced switch is a high priority manual switch by the networkoperator, failure of a working is a failure of a working tributary card32 and manual switch is a low priority manual switch by the networkoperator. It will be understood that other or different types ofrequests may be included within the requests hierarchy 82 in that therequests types may be otherwise suitably prioritized.

The equipment hierarchy 84 defines the priority of the working tributarycards 32 in the protection group 30. In a particular embodiment, thetributary cards are prioritized based on a card number such as card 1 tocard 6, channel reference number or other suitable reference oridentifier. In this embodiment, the tributary cards 32 may beprovisioned in order based on their priority. Alternatively, thetributary cards 32 may be provisioned and the protection order laterdefined in the equipment hierarchy 84.

FIG. 3 illustrates the state memory 62 in accordance with one embodimentof the present invention. In this embodiment, the states of the workingand protect tributary cards 32 and 34 are stored in a table 90. Thetable 90 includes a column for each working tributary card 32 and theprotect card 34 and a row for each type of protection activity. For thefinite state machine 60 of FIG. 2, the protection activities are forced,lockout, manual and automatic. A forced activity is a high prioritynetwork operator initiated activity, a manual activity is a low prioritynetwork operation initiated activity, an automatic activity is a anactivity generated automatically in response to a hardware or otherfailure or alarm and a lockout activity is an activity preventing use ofa card.

Referring to FIG. 3, a bit is set in each entry 92 of the table 90indicating the status of the corresponding card for the correspondingactivity. In a particular embodiment, the bits are set to zero in theabsence of the defined activity and set to 1 during the occurrence ofthe activity. It will be understood that the states of the working andprotect cards 32 and 34 in the protection group 30 may be otherwisesuitably stored in the protection controller 52 without departing fromthe scope of the present invention.

FIG. 4 is a functional diagram illustrating input to and output from thefinite state machine 60 in accordance with one embodiment of the presentinvention. In this embodiment, a network operator or other user 120initiates user protection requests 122 for any of the working tributarycard 32 and the protect card 34. The operator requests are received bythe user interface 50, translated and passed to the protectioncontroller 52 for evaluation.

The working or protect tributary cards 32 or 34 or other hardware 130each generate automatic requests 132 in response to card failures, alarmconditions and/or other suitable events and/or conditions of thehardware 130. As used herein, the phrase in response to means performingthe identified action directly or indirectly following the identifiedevent. Thus, the action may occur immediately or substantiallyimmediately upon the occurrence of the event or after another necessaryor intervening event.

The finite state machine 60 receives the operator requests 122 and theautomatic requests 132 and evaluates the requests based on priority ofthe requests and priority of the equipment for which the requests ismade to determine protection activity 140. The protection activity 140is output by the finite state machine 60 to the hardware 130 forperformance by the hardware. In this way, the protection activity isdetermined based on all of the operator and automatic request 122 and132 to provide optimized protection for any state of the protectiongroup 30.

FIG. 5 illustrates a method for processing protection request for an 1:Nprotection group in accordance with one embodiment of the presentinvention. The method begins at step 150 in which a protection requestsis generated. The requests may be generated by a network operator at aNMS or by hardware 130 in response to a failure, alarm condition orother suitable condition of the hardware.

Preceding to step 152, the requests is communicated to the protectioncontroller 52. For operator, or user, initiative request, the requestmay be translated by the user interface 50 before being passed to theprotection controller 52. Similarly, hardware initiated requests may betranslated prior to transmission to the protection controller 52 if notin the native language of the controller 52.

At step 154, the request is evaluated based on a priority of the requestand a priority of the equipment for which the request is generated. Asdescribed in more detail below, the request is evaluated by comparingthe priority of the request and of the equipment to the priority of allother requests for the same or other equipment in the protection group30. Next, at decisional step 156, the requests is activated if therequests comprises the highest priority among outstanding requests or,if more than one request is at the same highest priority level, therequest is for the highest priority equipment at that level. Thus, acurrently activated, lower priority protection request will bedeactivated. If the request is activated, the Yes branch of decisionalstep 156 leads to step 160 in which the requests is performed. At step162, the initiator is notified of the action taken, or results of therequest.

Returning to decisional step 156, if the requests is not activated, theNo branch of decisional step 156 also leads to step 162 in which theinitiator is notified of the result. Step 162 leads in the end of theprocess in which protection switching is provided based on the priorityof the requests and the priority of the equipment to optimize protectionswitching in an 1:N or other suitable protection environment.

FIG. 6 illustrates a method for monitoring an 1:N protection group andevaluating protection requests for the group in accordance with oneembodiment of the present invention. The method begins at state 200 inwhich the protection group 30 is monitored by the finite state machine60. In response to receipt of a protection request, state 200transitions to step 202. At step 202, the state memory 62 of theprotection group 30 is updated to reflect the request. The requests maybe an activation request or a deactivation request.

Proceeding to decisional step 204, the finite state machine 60determines whether any requests are outstanding. If no requests areoutstanding, no further processing is required and the No branch ofdecisional step 204 returns to the monitor state 200. If one or moreprotection requests are or remain outstanding, the Yes branch ofdecisional step 204 leads to decisional step 206.

At decisional step 206, the finite state machine 60 determines whetherthere are competing protection request for use of the protect card 32.If there is only one outstanding request, the No branch of decisionalstep 206 leads to step 208 in which the lone outstanding request isperformed. Upon performance of the protection request, step 208 returnsto monitoring state 200 such that protection status may be reevaluatedin response to any further requests.

At decisional step 206, if there are competing requests, the Yes branchof decisional step 206 leads to step 210 in which the outstandingprotection request having the highest priority is selected. In oneembodiment, the highest priority requests is selected based on therequests hierarchy 82 in which a failure of protection has a higherpriority than lockout of protection which has a higher priority thanforced switch, which has a higher priority than failure of working,which has a higher priority than manual switch.

Next, at decisional step 212, the finite state machine 60 determineswhether there are multiple requests at the highest priority. If only asingle requests is of the highest priority, the No branch of decisionalstep 212 leads to step 214. At step 214, the selected highest priorityprotection requests is performed. Step 214 returns to monitor state 200in which the finite state machine 60 continues to monitor the protectiongroup 30 for further request activity.

Returning to decisional step 212, if there are multiple requests at thehighest priority, the Yes branch of decisional step 212 leads to step216 in which the requests for the highest priority equipment among thehighest priority request is selected. At step 218, the selected requestsis performed for the selected equipment. State 218 returns to state 200in which the finite state machine 60 continues to monitor the protectiongroup for further protection requests.

In this way, the order of protection down to the request type and theequipment level may be specified by the network operator and carried outby the finite state machine 60. The finite state machine 60 willterminate protection of a low priority request and/or equipment in favorof a higher priority request and/or equipment. In addition, in responseto termination of the currently activated requests, the finite statemachine 60 will determine the next higher priority request and/orequipment and provide protection for that requests and/or equipment.Thus, protection switching is optimized for the 1:N protection switchingenvironment.

Although the present invention has been described with severalembodiments, various changes and modifications may be suggested to oneskilled in the art. It is intended that the present inventionencompasses such changes and modifications that fall within the scope ofthe appended claims and their equivalents.

1. A method for protecting equipment in a network element, by aprotection controller comprising: Receiving a first protection requestfor a first equipment item having a first equipment type, the firstprotection request having a first request type; Receiving a secondprotection request for a second equipment item having a second equipmenttype, the second protection request having a second request type;Determining by said protection controller a higher priority item betweenthe first and the second equipment items based on the first and thesecond request types and based on the first and second equipment types;and Performing by said protection controller the protection request forthe higher priority item.
 2. The method of claim 1, wherein theequipment items comprise line interface cards.
 3. The method of claim 2,wherein line interface cards each comprise a plurality of single userconnections.
 4. The method of claim 2, wherein the line connectioninterface cards each comprise only single user connections.
 5. Themethod of claim 2, wherein the line interface cards each comprise aplurality of DS-1 connections.
 6. The method of claim 2, furthercomprising determining the higher priority item based on an identifierof the line interface cards.
 7. The method of claim 1, furthercomprising: performing the first protection request for the firstequipment item in an absence of the second protection request for thesecond equipment item; determining the higher priority item in responseto receiving the second protection request for the second equipmentitem; and deactivating the first protection request for the firstequipment item in response to determining the second equipment item isthe higher priority item.
 8. The method of claim 1, further comprisingreceiving the protection request for at least one of the equipment itemsfrom a network operator.
 9. The method of claim 1, further comprisingreceiving the protection request for at least one of the equipment itemsautomatically in response to a failure of the equipment item.
 10. Logicstored in software embodied in a computer-readable medium and whenexecuted by the processor to: Receive a first protection request for afirst equipment item having a first equipment type, the first protectionrequest having a first request type; Receive a second protection requestfor a second equipment item having a second equipment type, the secondprotection request having a second request type; Determine a higherpriority item between the first and the second equipment items based onthe first and the second request types and based on the first and secondequipment types; and Perform the protection request for the higherpriority item.
 11. The logic stored in software and embodied on thecomputer readable medium of claim 10, wherein the equipment itemscomprise line interface cards.
 12. The logic stored in software andembodied on the computer readable medium of claim 11, wherein lineinterface cards each comprise a plurality of single user connections.13. The logic stored in software and embodied on the computer readablemedium of claim 11, wherein the line connection interface cards eachcomprise only single user connections.
 14. The logic stored in softwareand embodied on the computer readable medium of claim 11, wherein theline interface cards each comprise a plurality of DS-1 connections. 15.The logic stored in software and embodied on the computer readablemedium of claim 11, further comprising determining the higher priorityitem based on an identifier of the line interface cards.
 16. The logicstored in software and embodied on the computer readable medium of claim10, further operable to: perform the first protection request for thefirst equipment item in an absence of the second protection request forthe second equipment item; Determine the higher priority item inresponse to receiving the second protection request for the secondequipment item; and Deactivate the first protection request for thefirst equipment item in response to determining the second equipmentitem is the higher priority item.
 17. The logic stored in software andembodied on the computer readable medium of claim 10, further comprisingreceiving the protection request for at least one of the equipment itemsfrom a network operator.
 18. The logic stored in software and embodiedon the computer readable medium of claim 10, further comprisingreceiving the protection request for at least one of the equipment itemsautomatically in response to a failure of the equipment item.